why do pot holes form in roads after snow and ice, please?

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  • Anonymous
    1 decade ago
    Favourite answer

    Many Road crews apply salt to slippery surfaces in winter. The salt melts the ice and snow down to around 15 deg. The melted water dilutes the salt and it loses it strength to keep the water liquid. the water settles in cracks, crevices, and poorly sealed past pot-hole repairs. The weakened salt-water then freezes, (while still below a freezing temperature), causing the expanding action to fracture existing concrete and asphalt.

    Source(s): A small amount of water inside a solid round concrete ball will shatter it when the ball is completely frozen.
  • 1 decade ago

    When the snow falls, it melts and the run off water then fills cracks in the surface of the roadway [tarmac]. This melt water then freezes overnight and as we all know, ice expands. This expansion of the ice in the cracks in the road surface then leads to larger cracking. Small holes may appear where more ice forms and the same expanding process continues until we get bucket sized potholes.

    The road outside my house looks like we've have a bombing run, must be a couple of dozen two feet wide potholes.

    I expect the council will send round the usual team of navvies to fix the holes sometime in 2012 - we'll need to smarten the place up just in case anyone visits this part of London during the Olympics thing.

  • Anonymous
    1 decade ago

    The salt they put down and the friction from car tires melts the snow and ice. As water, it can get into even the tiniest cracks. THEN as the evening turns to night, there's less traffic and more cold weather moves in. That water freezes. What happens when water turns to ice? It expands, right?

    So, imagine it ... water in a tight crack or crevice suddenly begins expanding. It puts pressure on the the side of the crevice. Over time, this pressure causes new breaks and breaches. Cars and trucks compound the problem by running over them, breaking away bits of the road. The combination of the snow and cold, the salt, and friction, and the refreezing is quite effective.

    Instant potholes!

  • 1 decade ago

    Most roadways are built in layers, starting with compacted earth and gravel for drainage. Some older city streets may even have a subsurface of bricks. All of these layers are covered with asphalt, which is a gooey blend of tar, oil byproducts, curatives and aggregate gravel. In an ideal setting, this layer of asphalt repels rainfall and snow, forcing it into drains or the shoulder of the road.

    Potholes form because asphalt road surfaces eventually crack under the heat of the day and the constant stresses of traffic. These cracks allow snow and rainwater to seep into the underlying dirt and gravel. During cold winter nights, this water freezes and expands. Some of the dirt and gravel is pushed out as a result, leaving a hole when the water eventually melts. Drivers continue to drive over these unseen holes, putting even more stress on the thin asphalt layer covering them.

    Eventually, the asphalt layer over these divots collapses, creating the traffic hazards we call potholes.

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  • 1 decade ago

    pot holes form in roads mostly due to the expansion/contraction of moisture resident in the road surface.

    More accurately pot holes form because most municipalities do not proactively manage their transportation infrastructure; roads have a finite life span. They will erode over time, and nature will swallow up the asphalt. If not managed properly, a roadway can exceed its intended lifespan, and without repair or reconditioning will cease to provide the public with a surface suitable for wheeled vehicles.

    Source(s): US Dept of Transportation
  • 1 decade ago

    Sometime around early spring, many roads develop deep divots and pockmarks called potholes. Indeed, certain cities are said to have two seasons - winter and pothole repair. What causes these potholes to form, and why can't they be prevented in the first place? The answer involves both nature and the limitations of road construction.

    Most roadways are built in layers, starting with compacted earth and gravel for drainage. Some older city streets may even have a subsurface of bricks. All of these layers are covered with asphalt, which is a gooey blend of tar, oil byproducts, curatives and aggregate gravel. In an ideal setting, this layer of asphalt repels rainfall and snow, forcing it into drains or the shoulder of the road.

    Potholes form because asphalt road surfaces eventually crack under the heat of the day and the constant stresses of traffic. These cracks allow snow and rainwater to seep into the underlying dirt and gravel. During cold winter nights, this water freezes and expands. Some of the dirt and gravel is pushed out as a result, leaving a hole when the water eventually melts. Drivers continue to drive over these unseen holes, putting even more stress on the thin asphalt layer covering them.

    Eventually, the asphalt layer over these divots collapses, creating the traffic hazards we call potholes. Potholes can cause significant damage to a car's suspension system or tires if the driver fails to avoid them. Potholes can also fill with water, obscuring any other hazards they may contain. Even in places where the air temperature rarely falls below freezing, excessive rainfall or flooding can also cause potholes to form.

    Road maintenance crews have two different forms of repair methods for potholes. These repairs are roughly similar to a dentist using either a temporary or permanent filling material for cavities. During the winter months, potholes receive what is known as a cold winter mix. This is a temporary fix consisting of a soft asphalt poured into the potholes after they have been cleared of debris. A layer of gravel may be added to increase strength and stability, but the potholes are often expected to reappear by spring.

    A more permanent fix for potholes is called a hot summer mix. This combination of roadgrade asphalt and aggregate is designed to last for years, but it can only be applied during dry, warm weather. When road crews use a hot summer mix to repair potholes, they often reroute traffic around the worksite and spend more time preparing the road surface for the patch. The finished layer of new asphalt is usually compacted to match the level of the road, rendering it nearly invisible.

    Source(s): My Brain
  • Alex M
    Lv 5
    1 decade ago

    In addition to Mark H, I would add that snow plows also cause a lot of the damage, especially when the road is already damaged from the freezing and expanding water. Those metal blades wreck havoc.

  • Anonymous
    1 decade ago

    Water in small holes expands when it freezes and caused the cracks to widen and bits of the road to split making pot holes etc

  • 1 decade ago

    Water gets between the stones and tar in the road surface. When the water freezes it expands forcing the stones and tar apart. Traffic then moves these loose bits around and eventually a hole is formed.

  • 1 decade ago

    Water gets into tiny cracks and it freezes. Frozen water expands and causes the crack to get bigger. This happens over and over again until the road starts to crumble. Snow plows make it worse by driving overt it.

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